The present invention relates to a method for making organic carbonates such as diphenyl carbonate by effecting reaction of an organic hydroxy compound, such as phenol, with carbon monoxide and oxygen in the presence of an effective amount of a palladium catalyst and carbon dioxide as a desiccant. More particularly, the present invention relates to a continuous or batch method for making organic carbonates at elevated temperatures and pressures under neat conditions in the absence of a solid desiccant.
Prior to the present invention, aromatic carbonates, such as diphenyl carbonate were made by effecting reaction between phenol, carbon monoxide, an oxidant and a Group VIII element or catalyst. Aromatic carbonates are of interest to thermoplastic manufacturers, since they offer an alternative non-phosgene route to aromatic polycarbonates by melt transesterification. A procedure for making aromatic carbonates using an organic solvent, such as, methylene chloride, is shown by Chalk, U.S. Pat. No. 4,187,242. Additional procedures for making organic carbonates are shown by Hallgren, U.S. Pat. Nos. 4,361,519 and 4,410,464, utilizing a molecular sieve as a drying agent for the water formed during the reaction. Further procedures for making aromatic carbonates by catalytic carbonylation of aromatic hydroxy compounds, are shown by Japanese patent No. 01,165,551. Reference also is made to copending applications Ser. No. 17,248, filed Jul. 11, 1988, and Ser. No. 217,257, filed Jul. 11, 1988, utilizing a divalent or trivalent manganese salt or cobalt (II) salt and hydroquinone in combination with a palladium catalyst to catalyze the conversion of an organic hydroxy compound to an organic carbonate.
Although the aforementioned methods for making organic carbonates provide effective results in particular instances, the yields of the product are often less than 10%. In addition organic solvents are generally employed as well as solid drying agents which can interfere with the recovery of catalyst values.